When building design requires concrete walls a commonly used method for satisfying the need is concrete pre-cast wall sections. One of the popular systems available today is pre-cast concrete tilt-up wall panels. In reality the tilt-up system has been available in the U.S. for over ninety years. During this time the methods for fabrication and erection of the walls have changed little.
A concrete tilt-up wall is erected as the name implies. The wall section is first cast horizontally on some firm flat surface, usually the concrete floor of the building it is intended to support. In order that the concrete panel not adhere to the concrete floor, or surface supporting it, a commercially available chemical coating is first applied to the surface as a bond breaker. After the concrete has hardened to strength a heavy capacity lifting crane is employed to lift, or tilt, the wall section to a vertical position. The wall panel is set upon a concrete foundation or footing at which point it is temporarily supported until permanently incorporated into the structure it serves. The overall technique for casting and lifting is so basic little has changed in the methodology of tilt-panel work over decades.
One of the most labor-intensive portions of tilt-up panel construction is the forming and casting of the panel itself. After the casting surface, or floor, is available for panel forming, the crew lays out the shape of the tilt-up wall panel and proceeds to construct a perimeter bulkhead or screed system conforming to that layout. The method of fastening the bulkhead to the forming surface is by concrete nailing, or self-tapping screws set into pre-drilled holes. This bulkhead or screed is of a height that equals the thickness of the wall panel to be cast. Currently, and historically, the lumber and materials that are used to create this screed system are of dimensions for lumber and other common elements readily available on the commercial market. This by its nature makes forming dimensions a conform to 2.times.lumber width and thickness. The result is most tilt panels are as thick as the dimensions of the lumber. This generally limits engineering design to those wall thicknesses.
Further, when laying out the walls the normal vertical wall joint spacing when erected, usually 1/2" to 1", must be allowed for. This is because the bulkheads are made from 2.times.6, 8 or 12 inch lumber floor plates and vertical 2.times.6, 8 or 10/12 wood bulkheads all resulting in the cross section shape of an "L". This leads to calculating and adjusting allowance for various layout dimensions. The thickness dimension of the wall may be altered by adding to the bulkhead height in some fashion, all at additional cost.
A negative and costly feature of this generic method is that the forming materials often become expendable because of cutting, rough use and destruction during dismantlement of the formwork. Another poor feature of this system is that during construction and removal of the materials, using the current technique, damage is inflicted on the floor requiring extensive remedial patching and correction. In view of these and other limitations, there is a need for alternative methods and apparatuses that can address the limitations associated with the techniques currently practiced in the art. The invention provides such methods and apparatuses. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.